Nickel ink and conductor film formed of nickel ink

Abstract

A nickel ink having nickel particles dispersed in a dispersion medium is disclosed. The dispersion medium comprises one member or a combination of two or more members selected from the group consisting of an alcohol and a glycol both having a boiling point of 300° C. or lower at atmospheric pressure. The nickel particles have an average primary particle size of 50 nm or smaller. The nickel ink provides a conductor film with a surface smoothness having an average surface roughness Ra of 10 nm or smaller and a maximum surface roughness R max of 200 nm or smaller.

The invention claimed is: 
     
       1. An ink comprising:
 a dispersion medium, 
 a coupling agent, and 
 metallic particles consisting of nickel particles, 
 the dispersion medium comprising a main solvent, a surface tension modifier and a viscosity modifier, wherein: 
 the main solvent consists essentially of a glycol having a boiling point of 300° C. or lower at atmospheric pressure, and a viscosity of 100 cP or lower at ambient temperature, 
 the surface tension modifier consists essentially of an alcohol having a boiling point of 100° C. to 300° C. at atmospheric pressure and a surface tension of 20 to 34 mN/m at 25° C., 
 the viscosity modifier consists essentially of a ketone having a boiling point of 100° C. to 300° C. at atmospheric pressure, and 
 a weight ratio of the surface tension modifier to the main solvent is in a range of 0.1 to 0.5 and a weight ratio of the viscosity modifier to the main solvent is in the range of 0.1 to 1.2, 
 the coupling agent comprises one member or a combination of two or more members selected from the group consisting of a silane coupling agent, a titanium coupling agent, a zirconia coupling agent and an aluminum coupling agent, 
 the metallic particles consisting of nickel particles have an average primary particle size of 50 nm or smaller, 
 the weight ratio of the coupling agent to the nickel particles is in a range of from 0.05 to 0.6, and 
 the ink has a surface tension in a range of 15 to 50 mN/m and a viscosity at 25° C. of 60 cP or lower such that the ink is used for inkjet printing. 
 
     
     
       2. The ink according to  claim 1 , wherein the nickel particles have an average primary particle size of 10 to 30 nm. 
     
     
       3. The ink according to  claim 1 , wherein the nickel particles are prepared by heating a reaction mixture comprising a nickel salt, a polyol and a noble metal catalyst, the mixture being heated to a reaction temperature that reduces nickel ions. 
     
     
       4. The ink according to  claim 1 , wherein a total amount of the coupling agent and the nickel particles is in a range of from 5% to 40% by weight of the ink. 
     
     
       5. The ink according to  claim 1 , wherein a concentration of the coupling agent in the ink is in a range of from 1% to 48% by weight. 
     
     
       6. An ink comprising:
 a dispersion medium, 
 a coupling agent, and 
 metallic particles consisting essentially of nickel particles, 
 the dispersion medium comprising a main solvent, a surface tension modifier and a viscosity modifier, wherein: 
 the main solvent consists essentially of a glycol having a boiling point of 300° C. or lower at atmospheric pressure, and a viscosity of 100 cP or lower at ambient temperature, 
 the surface tension modifier consists essentially of an alcohol having a boiling point of 100° C. to 300° C. at atmospheric pressure and a surface tension of 20 to 34 mN/m at 25° C., 
 the viscosity modifier consists essentially of a ketone having a boiling point of 100° C. to 300° C. at atmospheric pressure, and 
 a weight ratio of the surface tension modifier to the main solvent is in a range of 0.1 to 0.5 and a weight ratio of the viscosity modifier to the main solvent is in the range of 0.1 to 1.2, 
 the coupling agent comprises one member or a combination of two or more members selected from the group consisting of a silane coupling agent, a titanium coupling agent, a zirconia coupling agent and an aluminum coupling agent, 
 the nickel particles have an average primary particle size of 50 nm or smaller, 
 the weight ratio of the coupling agent to the nickel particles is in a range of from 0.05 to 0.6, and 
 the ink has a surface tension in a range of 15 to 50 mN/m and a viscosity at 25° C. of 60 cP or lower such that the ink is used for inkjet printing. 
 
     
     
       7. The ink according to  claim 6 , wherein the nickel particles have an average primary particle size of 10 to 30 nm. 
     
     
       8. The ink according to  claim 6 , wherein the nickel particles are prepared by heating a reaction mixture comprising a nickel salt, a polyol and a noble metal catalyst, the mixture being heated to a reaction temperature that reduces nickel ions. 
     
     
       9. The ink according to  claim 6 , wherein a total amount of the coupling agent and the nickel particles is in a range of from 5% to 40% by weight of the ink. 
     
     
       10. The ink according to  claim 6 , wherein a concentration of the coupling agent in the ink is in a range of from 1% to 48% by weight. 
     
     
       11. An ink comprising:
 a dispersion medium, 
 a coupling agent, and 
 nickel particles, 
 the dispersion medium comprising a main solvent, a surface tension modifier and a viscosity modifier, wherein: 
 the main solvent consists essentially of a glycol having a boiling point of 300° C. or lower at atmospheric pressure, and a viscosity of 100 cP or lower at ambient temperature, 
 the surface tension modifier consists essentially of an alcohol having a boiling point of 100° C. to 300° C. at atmospheric pressure and a surface tension of 20 to 34 mN/m at 25° C., 
 the viscosity modifier consists essentially of a ketone having a boiling point of 100° C. to 300° C. at atmospheric pressure, and 
 a weight ratio of the surface tension modifier to the main solvent is in a range of 0.1 to 0.5 and a weight ratio of the viscosity modifier to the main solvent is in the range of 0.1 to 1.2, 
 the coupling agent comprises one member or a combination of two or more members selected from the group consisting of a silane coupling agent, a titanium coupling agent, a zirconia coupling agent and an aluminum coupling agent, 
 the nickel particles have an average primary particle size of 50 nm or smaller, 
 the weight ratio of the coupling agent to the nickel particles is in a range of from 0.05 to 0.6, and 
 the ink has a surface tension in a range of 15 to 50 mN/m and a viscosity at 25° C. of 60 cP or lower such that the ink is used for inkjet printing. 
 
     
     
       12. The ink according to  claim 11 , wherein the nickel particles have an average primary particle size of 10 to 30 nm. 
     
     
       13. The ink according to  claim 11 , wherein the nickel particles are prepared by heating a reaction mixture comprising a nickel salt, a polyol and a noble metal catalyst, the mixture being heated to a reaction temperature that reduces nickel ions. 
     
     
       14. The ink according to  claim 11 , wherein a total amount of the coupling agent and the nickel particles is in a range of from 5% to 40% by weight of the ink. 
     
     
       15. The ink according to  claim 11 , wherein a concentration of the coupling agent in the ink is in a range of from 1% to 48% by weight.